Based on the seismic data (Mw≥6.9) in Peru, according to the theory of commensurability, the signal intensity of the earthquakes tendency is analyzed and judged by using the methods of commensurability information. The butterfly structure diagram , commensurability structure system and epicenter migration approach are employed to prove the reliability of the forecast result and reveal how the astronomical factors effect strong earthquake activities. It shows that the seismic activities of Mw≥6.9 in Peru since 1970 exhibit obvious commensurability, the tendency of an intermediate focus earthquake occurring in 2019 is strong with the random probability of 55.56%. Besides, the great earthquakes in Peru have a significant relationship with the solar activity，earth's rotation and lunar movement: previous earthquakes mostly occurred in the solar activity peak and decline period, the double cycle of sunspot and the years with variance of the Earth's rotation rate; earthquake unlikely occurred in full moon and twilight moon days.